In current standard body width aircraft, such as the Boeing 737 and 757, the lower cargo compartments are primarily loaded by a bulk loading procedure. Bulk loading of individual nonstandard size pieces of cargo increases the number of pieces of cargo that must be handled between the aircraft and the freight terminal, require a relatively large number of ramp cargo handlers, and is very time consuming. All of these factors increase the cost of cargo handling, and the relatively long turn-around time for aircraft loading and unloading prevents maximum utilization of the aircraft. In addition, the lower cargo compartments in this type of aircraft have low compartment heights, forty-four to fifty-four inches, making moving cargo within the compartment difficult and even more time consuming. The combination of the difficulty in moving within the compartment and the large number of nonstandard size cargo pieces results in relatively inefficient use of the available cargo volume within the compartment.
An alternative to bulk loading is a conveyor system for handling containerized or pallet-mounted cargo. Such systems may take various forms. In one type of system, roller trays are located within recesses in the cargo compartment floor structure and pivot outwardly into a position for supporting cargo during the loading procedure. Another type of system has an electrically powered continuous belt installed within the aircraft for moving cargo units. In a third type of system, bulk cargo is loaded into telescoping bins which are built into the secondary structure of the aircraft. Each of these types of systems requires a sizable amount of interface between the aircraft systems and structure and the conveyor system during the manufacture of the aircraft. Therefore, the cost of providing the aircraft with the system is relatively high and retrofitting existing aircraft is at best impractical.
Cargo conveyor and restraint systems for aircraft are disclosed in French Pat. No. 1,062,462, granted to M. Henry and published on Apr. 23, 1954 and in U.S. Pat. No. 2,334,124, granted Nov. 9, 1943, to C. G. Peterson; U.S. Pat. No. 3,251,489, granted May 17, 1966, to R. W. Davidson; U.S. Pat. No. 3,357,372, granted Dec. 12, 1967, to H. E. Bader: U.S. Pat. No. 3,381,921, granted May 7, 1968, to F. M. McDonough et al.; U.S. Pat. No. 3,480,239, granted Nov. 25, 1969, to R. H. Jensen et al.; U.S. Pat. No. 3,741,504, granted June 26, 1973, to J. Alberti et al.; U.S. Pat. No. 3,899,092, granted Aug. 12, 1975, to A. B. Nordstrom; U.S. Pat. No. 3,906,870, granted Sept. 23, 1975, to J. Alberti; U.S. Pat. No. 4,000,870, granted Jan. 4, 1977, to D. J. Davies; and U.S. Pat. No. 4,077,590, granted Mar. 7, 1978, to T. H. Shorey. Latching mechanisms for cargo systems are disclosed in U.S. Pat. No. 3,759,476, granted Sept. 18, 1973, to W. H. Goodwin, and U.S. Pat. No. 4,134,345, granted Jan. 16, 1979, to F. G. Baldwin et al. U.S. Pat. No. 4,462,493, granted July 31, 1984, to A. B. Nordstrom, discloses a roller rail assembly for a cargo loading system.
The Davidson patent discloses a system in which several longitudinal lines of roller trays are directly attached to the floor structure of the cargo compartment. The outboard trays carry side guides which are laterally adjustable to accommodate different sized pallets. The trays in each of the lines carry vertical and longitudinal restraints.
The Bader system includes two lines of rollers and opposite outboard rails. The rows of rollers and the rails are each separately mounted directly to the floor. The rails carry latches and engage the edges of a pallet in slots to restrain the pallet.
Jensen et al. disclose a convertible cargo/passenger system having a plurality of lines of roller assemblies attached directly to the floor structure. Opposite side guides are also attached to the floor structure and to a carpet support. The roller assemblies and side guides in each line are longitudinally spaced, and latches are mounted to the floor between roller assemblies and between side guides. The side guide members carry rollers and have an outboard supporting leg.
Alberti et al. disclose an apparently permanent system having power driven conveyor wheels. The system includes side assemblies having cargo restraint locks and vertically facing guide rollers. The side locks permit limited fore and aft sliding movement of containers to maintain the flexibility of the aircraft by ensuring that the container is not so rigidly attached that it becomes a part of the aircraft structure.
Nordstrom, U.S. Pat. No. 3,899,092, discloses a load carrying system for use when cargo units do not span two or more floor tracks. The purpose of the system is to avoid overloading lightweight floor panels. The system has modules each of which includes transverse beams that are attached to permanent floor tracks and longitudinal beams attached to the transverse beams. Both the longitudinal beams and the transverse beams are spaced above the floor. Separate roller tray units are supported on the floor between the beams by resilient elastomeric strips. The roller trays normally carry cargo loads and distribute the loads over the floor. Under high loads, the resilient strips compress, and cargo units bottom out on the longitudinal beams so that the longitudinal and transverse beams carry the load. Cargo restraint means is mounted on the longitudinal beams.
The Shorey system includes a plurality of longitudinally spaced lateral bars that are attached to the seat tracks. The lateral bars have tie-down brackets. Panels are attached to the lateral bars and are spaced above the floor. The panels carry retractable inboard and outboard guide rails, cargo restraints, and roller assemblies.
The patent literature includes a number of examples of pallets and cradles for handling cargo and other articles. U.S. Pat. No. 2,833,501, granted May 6, 1958, to F. H. Evans, discloses a cradle-like handling and storage bolster for elongated metal objects. The bolster has opposite end members which curve upwardly at their extremities to support opposite ends of lengths of metal and which are formed from hollow shells filled with a concrete mixture. U.S. Pat. No. 3,430,586, granted Mar. 4, 1969, to W. N. Oswald, discloses a forklift and sling pallet for airborne ordnance. The pallet is corrugated for strength and for engaging a forklift and has sloping sides for strength, nestability, and flexibility in handling different sizes and configurations of weapons. U.S. Pat. No. 3,472,363, granted Oct. 14, 1969, to R. B. Rustin, Jr. et al., discloses a container base/pallet having sloping sides to engage a cylindrical article. U.S. Pat. No. 3,753,407, granted Aug. 21, 1973, to A. B. Tilseth, discloses a cradle-like pallet having a pair of triangular truss-like reinforcing elements for supporting cylindrical cargo and straps for securing the cargo. A corrugated inverted channel floor insert may be positioned over the reinforcing elements to convert the pallet to a configuration for carrying noncylindrical articles. U.S. Pat. No. 4,382,733, granted May 10, 1983, to K. G. Rodgers, discloses a cradle for carrying an engine which includes a pair of longitudinal members and a pair of U-shaped padded lateral members for supporting the engine.
The above patents and the prior art that is discussed and/or cited therein should be studied for the purpose of putting the present invention into proper perspective relative to the prior art.